Computation of mixed mode stress intensity factors in a four-point bend specimen

Four-point bend specimen is one of the most important specimens of the fracture mechanics because it can produce mixed modes I and II. Therefore, computation of stress intensity factors in this specimen is of practical interest. Several relations have been suggested that no one of them has completely considered the effects of the loading point and crack geometry. In this paper, mixed mode stress intensity factors of the bend specimen are computed by finite element method (FEM) and after validating by comparing with the available results in the literature, the results will be assessed to determine the effects of different crack location and loading distances from the middle of the specimen. Finally, two new coefficients comprising these effects are introduced.     

M?ssbauer spectroscopy in heterogeneous catalysis: A brief overview and recent study on paramagnetic features detected in catalytic centres of Fe-ZSM-5

A short retrospection is given on the development of M?ssbauer spectroscopy and on the early period of its application to heterogeneous catalysis in Hungary. Besides the historical view, we present results of recent studies of a latest application on a nanosystem. Namely, catalytic centres in Fe-ZSM-5 are studied by in situ spectroscopy, the results are correlated with parallel activity measurements in the decomposition of N₂O. Changes in paramagnetic relaxation features are interpreted as the effects of Fe²⁺/Fe³⁺ interconversions. From the analysis, the dominance of the mononuclear species is suggested at lower temperature (620 K). The dinuclear Fe⁽³⁺⁾ _framework-O-Fe⁽²⁺⁾ _{extra-framework} species play probably more expressed role at higher temperatures (∼ 770 K) in the decompositon of nitrous oxide.     

Polyhedral approximation and practical convex hull algorithm for certain classes of voxel sets

In this paper we introduce an algorithm for the creation of polyhedral approximations for certain kinds of digital objects in a three-dimensional space. The objects are sets of voxels represented as strongly connected subsets of an abstract cell complex. The proposed algorithm generates the convex hull of a given object and modifies the hull afterwards by recursive repetitions of generating convex hulls of subsets of the given voxel set or subsets of the background voxels. The result of this method is a polyhedron which separates object voxels from background voxels. The objects processed by this algorithm and also the background voxel components inside the convex hull of the objects are restricted to have genus 0. The second aim of this paper is to present some practical improvements to the discussed convex hull algorithm to reduce computation time.     

On subnormal subgroups of linear groups

We describe the subnormal subgroups of 2-dimensional linear groups over local and full rings in which 2 is invertible, as well as the subnormal subgroups of symplectic groups over local rings in which 2 is invertible.     

Decomposition and removability properties of John domains

In this paper we characterize John domains in terms of John domain decomposition property. In addition, we also show that a domain D in ℔ ⁿ is a John domain if and only if D\P is a John domain, where P is a subset of D containing finitely many points of D. The best possibility and an application of the second result are also discussed.     

Modeling of non-stationary ground motion using the mean reverting stochastic process

This paper presents a new method for modeling amplitude and frequency non-stationary earthquake ground motions using a scalar first order dynamic mean reverting stochastic differential equation driven by Brownian motion with parametric time varying coefficients. It determines the proper relationship between these time varying parametric coefficients and presents the statistical and probability distribution characteristics of the response solution. It demonstrates the applicability of the method by presenting some simulations of amplitude and frequency non-stationary earthquake ground motions. The verification of the amplitude and frequency non-stationary contents of the mean reverting stochastic ground motions is demonstrated using the Hilbert–Huang transform method. Also a corresponding interpretation between the coefficients of the proposed model and the coefficients of the usual oscillatory second order differential equation driven by white Gaussian noise is presented along with some comments how it can be applied to simulate ground motions consistent with acceleration target records such as boxcar, trapezoidal, other exponential functions, or compound and target records at source, near field, and far field distances.     

Preparation and evaluation of ammonia decomposition catalysts by high-throughput technique

The high-throughput technique has been successfully employed to investigate systematically NH₃ decomposition catalysts for COx-free hydrogen production. Supported γ-Mo₂N catalysts not only could be prepared and evaluated by the high-throughput experiment, but are also active for NH₃ decomposition luke supported Ni and Co catalysts. Additionally, the preparation process and support play important roles on the catalytic performance of supported γ-Mo₂N catalysts.     

Optimal superconvergent one step quadratic spline collocation methods

We formulate new optimal quadratic spline collocation methods for the solution of various elliptic boundary value problems in the unit square. These methods are constructed so that the collocation equations can be solved using a matrix decomposition algorithm. The results of numerical experiments exhibit the expected optimal global accuracy as well as superconvergence phenomena. AMS subject classification (2000)  65N35, 65N22     

Thermal decomposition of butylindium thiolates and preparation of indium sulfide powders

Thermal properties of organoindium thiolates were investigated by means of thermogravimetric (TG) and differential thermal (DT) analysis. Dibutyl-indium propylthiolates (Buⁿ₂InSPrⁿ, Buⁿ₂InSPrⁱ, Buⁱ₂InSPrⁿ and Buⁱ₂InSPrⁱ) decomposed up to 280°C along with an exothermic DT peak and gave indium(I) sulfide (InS) powders. Although the arylthiolate Buⁿ₂InSPh also afforded InS powders, it decomposed at a slightly higher temperature. In contrast, the dithiolate and the dithiocarbamate complexes [BuⁿIn(SPrⁱ)₂ and In (S₂CNBu₂)₃] gave indium(III) sulfide (In₂S₃) powders.     

多频声光互作用的研究

本文推导出包括正常和反常声光互作用在内的多频声光耦合波方程的普适形式,并得出两个独立超声波信号时布拉格状态下方程的解.分析了多频声光互作用的各种线性和非线性效应,包括衍射效率、压缩、交叉调制和各级互调制强度等,并指出反常与正常多频声光衍射的差异.结论是反常多频声光互作用情况下,各级互调制模强度与主衍射模强度的比值小于正常多频声光互作用情况下的相应比值.实验结果与理论分析相符.